MINNEAPOLIS - The morning rush at Minneapolis - St. Paul International Airport is always a semi-chaotic scene, with passengers inside the terminal rushing to get to their gates, and controllers and pilots executing a carefully choreographed routine to get airplanes down the runways and into the air with little delay.
Throw snow or ice into the mix, and the dynamic changes drastically.
That's because ice is aviation enemy number on in northern climates during the winter months. The clingy frozen substance contaminates and disturbs air flow on surfaces like a plane's fuselage, wings and tail, which are carefully designed to be smooth and aerodynamic.
"it's weight, it adds drag and also it affects the lift of the airplane, so the airplane isn't as efficient," explained Jeffrey Hart, Delta's General Manager for Airport Services."The FAR, Federal Air Regulations, require a clean aircraft before departure, so all contaminants have to be removed from that airplane before it departs, in this case ice and snow."
In extreme cases, when ice builds up… it can bring planes down. NASA researchers have blamed icing for nearly 10 percent of fatal air carrier accidents. That's why Delta Airlines' Twin Cities hub commits thousands of man hours and millions of dollars each year to de-icing operations… to make sure airplanes and passengers reach their destinations safely.
"We never want to see an airplane take off with contaminants on the wing, because it's a potential unsafe situation," said Hart.
At Delta, the decision to de-ice or not ultimately falls on the captain at the controls of each flight, pilots like Captain Scott Bowles.
"Along the front edge of the wing a lot of times we'll see what we call rime ice that will develop," Bowles explained to KARE 11 Meteorologist Belinda Jensen as they walked around a Delta Airbus on a snowy January day.. "That's moisture that will melt and freeze on the last approach the airplane flew."
Bowles and other pilots do their pre-flight walk-around about 30 minutes before takeoff to make sure the plane is airworthy, and to check for the presence of snow or ice, especially on the wings and tail. As we circle the airbus conditions begin to change abruptly.
"Obviously today is a day where things have been changing hour to hour, now we have ice falling," Bowles told Jensen, "so now most likely the crews will require de-icing."
On mornings where temperatures are below freezing and aircraft surfaces may be coated with frost or light ice, two-person teams will board bucket trucks loaded with heated propylene glycol and treat the fuselage, wings and tail of outgoing planes. This was one of those days.
"We're up almost every day either due to frost, light snow, what have you here in Minnesota," said De-ice pad controller Brian Dotson.
Things shift into high gear on this day, as weather conditions quickly deteriorate into a ground blizzard. Pilots radio the 'icemen' at the airport control center tower, who steer them to one of two full-service de-icing hubs to be de-iced just before takeoff. When heavy snow or ice is falling, a second coat of more concentrated glycol is sprayed to prevent ice from re-forming.
Trucks can also be dispatched to spray aircraft after they pull back from the terminal gate, to minimize wait lines and delays, which have a direct impact on customer's schedules.The operation is a ballet of gangly trucks and giant aluminum birds, choreographed by de-icing tower crews, and performed by more than 200 specially trained employees like Tom Fischer and Vern Hammersten.
"When he gives me the command we just head on down the wing," explained Fischer. "The icing fluid steams up, so I have to make sure his bucket doesn't get too close to the airplane."
A light de-icing treatment can be done in as little as 3 to 5 minutes. Removing heavier ice or snow in the wake of a major winter storm can take 25 to 30 minutes. It is a process that tests passenger patience in a hurry-up world, but taking shortcuts is an option Delta will not consider.
"We may take a little bit of extra time to do that, but what we're trying to do is provide for their safety and ensure that the airplane is safe before it takes off," insists Delta's Jeff Hart.
It is not a cheap routine: Last de-icing season, which ran from September of 2012 to May of 2013, Delta spent $10.3 million on Glycol alone.